Tetrakis (fluoroaryl) borate is a compound which is useful as (a) a co-catalyst of a metallocene catalyst (polymerization catalyst) used in a cation complex polymerization reaction or (b) a catalyst for siloxane photopolymerization.
A tetrakis (fluoroaryl) borate. magnesium compound is produced by reacting fluoroaryl magnesium halide with a boron compound for example. As the boron compound used in the reaction, boron trifluoride is exclusively used in industrial production due to its usability. As to a molar ratio of the fluoroaryl magnesium halide and the boron compound upon producing the tetrakis (fluoroaryl) borate. magnesium compound, Japanese Unexamined Patent Publication No. 295984/1997 (Tokukaihei 9-295984)(Publication date: Nov. 18, 1997) discloses, for example, that: fluoroaryl magnesium halide is reacted with the boron compound so that a molar ratio of the fluoroaryl magnesium halide is not less than 4.0 mol and not more than 5.0 mol with respect to 1 mol boron compound. While, Japanese Unexamined Patent Publication No. 191666/2000 (Tokukai 2000-191666)(Publication date: Jul. 11, 2000) discloses that: it is preferable to react the fluoroaryl magnesium halide with the boron compound so that a molar ratio of the fluoroaryl magnesium halide is not less than 3.5 mol and is not more than 5.0 mol with respect to 1 mol boron compound, and it is more preferable to react fluoroaryl magnesium halide with the boron compound so that a molar ratio of fluoroaryl magnesium halide is not less than 3.7 mol and is not more than 4.5 mol with respect to 1 mol boron compound.
As to the method for producing the tetrakis (fluoroaryl) borate. magnesium compound, the method using boron trifluoride as the boron compound generates not only tetrakis (fluoroaryl) borate. magnesium compound but also magnesium compound which contains fluorine atom as a by-product. Then, treating the reaction mixture with acid in order to remove the magnesium compound, hydrogen fluoride which corrodes a producing apparatus is generated. Thus, the method for producing the tetrakis (fluoroaryl) borate. magnesium compound requires a special apparatus, so that this is not preferable in industrial production.